Semi-active radar homing (SARH) is a common type of missile guidance system, perhaps the most common type for longer-range air-to-air and surface-to-air missile systems. The name refers to the fact that the missile itself is only a passive detector of a radar signal—provided by an external ("offboard") source—as it reflects off the target. Semi-active missile systems use bistatic continuous-wave radar.
Figure 1. Semi-active radar homing flight path geometry.
9B-1101K, inertial semi-active homing head for R-27R missiles.
Missile guidance refers to a variety of methods of guiding a missile or a guided bomb to its intended target. The missile's target accuracy is a critical factor for its effectiveness. Guidance systems improve missile accuracy by improving its Probability of Guidance (Pg).
A guided bomb strikes a practice target
Israel's Arrow 3 missiles use a gimbaled seeker for hemispheric coverage. By measuring the seeker's line-of-sight propagation relative to the vehicle's motion, they use proportional navigation to divert their course and line up exactly with the target's flight path.
Inspection of MM III missile guidance system